The best method is multiple solutions. Hard drives fail, devices break etc. -- If you truly want to have a copy of these video files in 10, 20, or 30 years then the best solution is to backup using 2-3 different methods. Using a FTP like people recommend is a good solution, DVDs (stored in a secure box (preferably a fireproof one or one stored at a bank/similar,)) and keeping a external hard drive with a copy of the files means that if the server that you are hosting gets hacked into and all of the files deleted, your house burns down with all of your stuff inside then you still have a copy elsewhere and you don't lose those videos forever.

With Facebook, you are guaranteed to NEVER, EVER, have it deleted.